Dragline excavator



F b- 21, 19 1 'r. LEARMONT 2,972,199

DRAGLINE EXCAVATOR Filed Oct. 30. 1958 2 Sheets-Sheet 1 mar E6}.

WWMMM INVENTOR, Tom LEARMONT ATTORNEY Feb. 21, 1961 LEARMONT 2,972,199

DRAGLINE EXCAVATOR Filed Oct. 50, 1958 2 Sheets-Sheet 2 INVENTOR, TomLEAR MONT ATTORNEY United States Patent DRAGLINE EXCAVATOR Tom Learmont,Wauwatosa, Wis., assignor to Bucyrus- Erie Company, South Milwaukee,Wis., a corporation of Delaware Filed Oct. 30, 1958, Ser. No. 770,742

9 Claims. (Cl. 37-116) This invention relates to dragline excavators,particularly the boom construction and suspension means. It isparticularly adapted to ovecome the problems of recoil of the boomcaused by a sudden release of the hoisted load and the reaction forcesin the boom and suspension.

It is the usual practice in boom construction for draglines to employ anintegral boom, of a given length, pivoted at its foot on a main frame,and to support the boom near its outer end by suitable suspensiontackle. The suspension tackle is anchored to the main frame and isusually trained over a mast, A-frame or other means, to provide agreater moment arm about the boom-foot pivot.

With such construction, any sudden release of a hoisted load results ina recoil of the boom and suspension tackle because of reaction forces inthose components. This recoil causes a flexing of'the intermediateportion, particularly the central portion, of the boom; if a severerecoil is encountered, or if a sufiicient number of flexing stresses areencountered repeatedly, failure of the boom will result.

An obvious method of overcoming this problem is to provide asufiiciently rigid boom and thereby prevent any critical flexing of thecentral portion; however, this results in a boom construction of suchweight as to reduce the efiiciency of the machine.

Therefore, it is the principal object of the present invention toprovide a dragline excavator with a boom and suspension means in whichthe boom is of great length in relation to total weight and overcomesthe problems associated with boom recoil.

In the past, certain types of boom constructions have been devised tominimize bending stresses in the central portion of. along boom.Examples of such constructions are disclosed in U.S. Patent No.2,015,629 to Knox and in US. Patent No. 2,080,163 to Busick. Both ofthese have worked out a number of novel and useful details,

which will be readily evident as the description progresses. Myinvention consists in the novel parts and in the combination andarrangements thereof, which are defined in the appended claims, and ofwhich different embodiments are exempllfied in the accompanying drawingswhich are hereinafter particularly described and explained.

Throughout the description, the same reference number is applied to thesame member or to similar members.

Figure 1 is a side elevation of one embodiment of my invent.onillustrating a dragline excavator in which the boom has been elevated toa working height.

Figure 2 is the same as Figure 1, except that the boom is in asubstantially horizontal position.

Figure 3 is a side elevation of another embodiment in which the boom iselevated to a working height.

Figure 4 is like Figure 3 except that the boom is in a substantiallyhorizontal position.

' Referring to Figures 1 and 2 which illustrate the first embodiment ofthis invention, a dragline excavator is shown having a main supportingframe 10 as a supporting base to which a boom and suspension can beattached. A boom 11 is pivotally supported at its foot on the main frameby a suitable pivot pin 12 to permit angular movement of the boom aboutthe pivot in a vertical plane.

The boom 11 comprises an inner section 13 and an outer section 14pivotally connected to each other by a joining pin 15. Anupwardlyinclined strut or mast 16 is pivotally connected to the inner boomsection 13 intermediate the ends of the inner section. The mast-toboomconnection may be any suitable means such as pin 17; however, thelocation of this mast-to-boom connec- 1 tion 17 must be spaced asufiicient distance outboard from patents illustrate a type of boomdesigned specifically shovel, that boom. section which supports theshipper shaft requires a rigid member of the boom suspension means, tobe connected to that same boom section at a point closely adjacent theshipper shaft. This member must be rigid since it withstands compressionforces caused by reaction of the dipper stick during crowdingoperations. In a dragline excavator such reaction forces are notencountered; and consequently rigid, heavy boom constructions, such asthose illustrated in the above Knox and Busick patents, are unnecessaryas well as'undesirable.

Therefore, it is also an object of the. present invention tozprovide adragline excavator with a multiple-section boom. and suspension whicheliminates the need for any heavy, rigid member or strut at the junctureof the boom the boom-foot pivot 12 and the mast must be inclined inrelation to the boom to result in a downward moment about the boom pivot12 acting upon the inner section 13 when the boom is in an elevatedworking position such as is shown in Figure 1. At the same time, thelocation of the connection 17 should not be placed so far out-' board asto result in excessive bending stresses on the inner section.

Suspension means for the boom is provided by suspension tackle,indicated at 18, between an anchorage 19 and the boom 11. The anchoragefor the suspension tackle 18 is carried on the main frame at an elevatedpoint above the boom pivot 12; as illustrated, the anchorage 19comprises cable reeling apparatus operably connected to a cable windingdrum 2t? and mounted preferably upon an A-frame or gantry 21. Thesuspension means may be of fixed-length tension members, such as ropes,cables,

rods or the like, but preferably includes variable-length,

boom-hoist tackle indicated at 18a connected between the anchorage 19and the upper end of the mast 16, and a fixed-length tension member1812, such as a rope or cable, connected between the top of the strut 16and the outer boom section 14 adjacent the boom point. Inter-' PatentedFeb. 21, 1961v position.

' members 1% and 130 of the suspension means are both of fixed lengthand preferably consisting of flexible ropes or cables. Since therelative lengths determine, to a certain degree, the alignment of thelongitudinal axes of the inner and outer boom sections 13 and 14 it isextremely important that these relative lengths be fixed afterdetermining the proper proportionate dimensions.

With the boom 11 and suspension means employed in a dragline excavatorstructure as shown, a load hoist line 23 is operably connected to asecond cable winding drum 24 on the main frame. The load line is thentrained over guide sheaves 25 supported on the boom and thence about aboom pointsheave 26 to be attached to a drag bucket 27 by suitable meansgenerally indicated at 28 A drag rope or cable 29 is also attached tothe bucket 26 by chains 30 and is also operably connected to a thirdcablewinding drum 31. a v

The main frame 16 may be supported on any suitable ground engagingmembers indicated conventionally at 32 andis usually provided withpropelling means (not shown) as well as means to rotate the main frameabout a center support (not shown) which remains fixed in relation tothe ground engaging members.

It can be seen that the mast 16 is interposed between the suspensionmeans 18 and the boom 11 to provide a greater boom suspension moment armabout the boomfoot pivot 12 and thereby decrease the force required toraise the boom and to support it in the elevated position shown inFigure l. The length of the mast 16 in relation to the length of theboom 11 is also dimensioned to provide a satisfactory angle between thesuspension means 18b and the boom to thereby minimize the compressionforces in the boom in any position without the use of such a long mastwhich would cause a shallow angle between the mast and its suspensiontackle 18a. The respective locations of the anchorage 19, the boom pivot12, and the mast-to-boom connection 17 as well as the length of the mast16 are also proportioned to provide a relativelywide angle between themast 16 and the suspension means 18a strung between the anchorage 19 andthe mast when the boom is in a substantially horizontal position shownin Figure'Z and to substantially maintain such wide angle when the boomis raised to the position shown in Figure 1. Since the compressionforces in structures such as booms and masts, which are pivoted at theirinner end and'supported by means of tension members at their outer ends,is proportional to the relative angle between such structure and thetensiontmember, it is imperative that this angle'be established at asatisfactorily wide angle and substantially maintained throughout therange of movement. With the structure shown, a relative angle in therange of 25 to 40 degrees has been determined to be satisfactory to keepcompressive forces in the boom and mast at a suficiently lowtvalue andthereby permit the use of lighter constructions and increase theover-all efficiency of the dragline excavator. This proportionatedimensioning of and location of these elements results in lowercompression forces in the mast 16. Thus it can be seen that a structurehas been devised which minimizes compression forces in the boom and alsoin the mast when the boom is substantially horizontal, a position whenmaximum compression forces are usually encountered in those members, aswell as when the boom is in raised Consequently, this wide angle ismaintained substantially throughout the range of working elevations ofthe boom when employed in a dragline excavator. The preferable range oflocations of the mast-to-boom connection 17 and the inclination of themast 16 relative to the boom 11 is such that the moment arm about theboom-foot pivot 12 of the line of action through the mast is not lessthan one-tenth A nor greater than one-half /2) of the moment arm of theline: of action of the intermediate suspension member 18c supporting theouter end of the inner boom section 13. By employing a mast so locatedand so inclined within the above range, a downward moment acting uponthe inner section 13 of the boom is insured without imposing excessivebending stresses on the inner section.

By referring to Figure 2, a dragline excavator is provided with a boomand suspension means utilizing short er, lighter components thanconventional draglines which a have integral booms and in which the mastis located adjacent the boom foot. With the present invention thecomponents may be positioned and handled-easily during assembly anderection of the boom. The usualsequence is to-first join the innersection 13 to the main base and then connect the outer section 14 to theinner section 13. One end of the mast 16 is pivotally connected to theboom at 17 and the suspension means 18a is strung between the anchorage19 and the free end of the mast and attached to cable drum 20. Theflexible ten- 1 si'o'nmember 18b,of fixed length, maythen be connectedbetweerithe variable length tension member 18a and the boom near theboom point. The flexible, fixed length tension member 18c should then beattached at one end to the mast 16, preferably near the top of the mast,and at the other end at a point 22 adjacent the connection 15 of theboom sections.

Subsequent operation of the cable-winding drum 20 will reel in cable of18a to shorten the length of suspension member 18a to raise the mast 16to a position where members 18b and 180 are in tension; furtherreeling'in of the cable of 18a will elevate the boom as shown in-Figure 1. e 1

' The length of the mast 16, the tension'members 18b and 180 and theouter section 14 as well as the inclination of the mast in relation tothe boom are proportioned so as to result in substantial alignment ofthe longitudinal axes of both boom sections 13 andl.

Referring to Figures 3 and 4, another embodiment ofthe invention isillustrated as having a boom 11 pivotally supported by the main frame10, and suspension means 18 strung between a connection with the boomadjacent the boom point and an elevated anchorage 19. A mast 16a isconnected between the suspension means and the boom and intermediatesuspension means 18c between the mast 16a and the boom are providedbeing connected to the intermediate portion of the boom at 22. Anysuitable hoisting mechanism may be provided which includes acable-winding drum and a load hoist line operably attached to the drumand trained over a boom point sheave such as illustratcd'in Figures 1and 2. To more clearly illustrate the boom and suspension means, none ofthe hoisting mechanism is shown in Figures 3 and 4.

in this embodiment the boom 11 comprises an inner section 13a and anouter section 14 pivotally connected to each other at 15. The innersection 13a is of trussed skeleton construction in the form of atriangle having a broad base and includes an apex 17a intermediate theends of the inner section 13a. The preferred embodiment positions'thisapex 17a closer to the boom-foot pivot 12 than the outer end ofsection'13a. The position of 17a is selected to provide a location for amast-to-boom connection 17 which will increase the vertical stability ofthe inner section without imparting critical bending stresses to thismember.

The mast 16a is also of trussed construction and preferably ispositioned, as shown in Figures 3 and 4, as an inverted triangle havingan apex 16b connected to the boom angular mast 1 6a, the lengthoftheboom T11 and the -respective locations of the anchorage 19, theconnection between the suspension means and the boom, the boom pivot 12and the mast-to-boorn connection 17 are so proportioned thatapproximately equal angles 21 and b."- result between the base 160 ofthe triangular mast and lines drawn through the lines of action of thesuspension members 18a and 18b on both sides of themast when the boom isin an elevated operating position. The forces down each leg of thetriangular mast and the truss construction of the mast result in bothlegs supporting each 7 other as a column. Consequently, the"compressiveload is imposed on a construction which is the equivalent of a straightcolumn thus eliminating any tendencyto buckle. By forming the innersection 13a of the boom 11 as a triangle and by locating themast-to-boo'rn connection at the upper apex 17a of this triangle,themast components are thereby shortened. This results in a more rigidmast which reduces the total weight on the boom and'consequently thefront end moment of the entire machine.

The mast 16a need not be constructed entirely of rigid struts since thebase 16c encounters tension stresses only. Therefore the mast 16a maycomprise a plurality of struts angularly spaced in a verticallongitudinal plane of the boom and each of the struts connected at oneend to the inner boom section by means of the mast-to-boom connection17. The upper ends of the struts may be connected by a portion of thesuspension means 18 and stiffening members interposed between the strutsto interconnect the struts at a plurality of points intermediate theends of the struts. Thus the forces down each strut and the stiffeningmembers interconnecting the struts result in the struts supporting eachother as a column and reduces any tendency to buckle.

In both Figures 2 and 4, the forms of the inventiondisclose a boom andsuspension means which provide a relatively wide angle between the mastand that portion of the suspension means 18a between the mast and theanchorage 19. This wide angle is desirable since compression stressesare thereby decreased in the mast. Conventionally constructed boomsuspensions locatethe mast on or adjacent the main frame resulting in arelatively short distance between the anchorage and the lower end of themast. By locating the mast-to-boom connection outwardly a suflicientdistance on the boom so that the distance between the anchorage 19 andthe mast-to-boom connection 17 is greater than the distance between theanchorage 19 and the boom pivot 12 when the boom is substantiallyhorizontal, a relatively wide angle is pro-' vided between the mast andthat portion of the suspension means 18a between the mast and theanchorage. This reduces compression stresses in the mast and permits theuse of a lighter weight mast construction.

The dragline excavators provided with the boom and suspension systemsshown in Figures 1 and 3 overcome the objectionable results caused byboom recoil upon a sudden release of the hoisted load, as in draglineoperation. Both constructions illustrated are capable of supporting ahoisted load by means of a suitable load hoist line such as 22 inFigure 1. The load line is in turn supported at the boom point bycooperation of the boom 11, the suspension means 18, anchorage 19, mast16 or 16a, and the main frame 10. The weight of any hoisted bucket andload tends to stretch the tension members 18a, 18b, and 18c of thesuspension means and tends to deflect downwardly the outer section 14 ofthe boom 11; the degree of deflection being determined by the relativeelasticity of these members in relation to total weight.

Dumping the bucket during conventional dragline operations causes asudden release of the strain energy present in the tension members 18a,18b and 180 during the loaded condition, as well as a release of theenergy in the slightly-deflected boom section 14. This sudden release ofenergy results in a reaction known as boom recoil and .causes theouterend of the outer section 14 to whip .upwarfdly. Since tension member 18bis flexible and boom section 14 is pivotally connected at 15 to theinner section, the boom recoil forces can be dissipated in the outerboom section. As the outer section returns from its recoiled position toits static unloaded position, an upward secondary reaction force isimparted to the inner end of section 14 and the entire boom tends tojackknife at the pivotal connection 15. However, since the Weight of themast and the weight of the supported components of the suspensionsystem, as well as the resultant of the suspension forces acting downthe mast, are all carried by the innerboom section 13, a downward momentis-imparted at all times to the inner section. Consequently, anytendency of the boom to jack-knife is prevented by the'stability of theinner section 13. A dragline excavator is thus provided with a boomconstruction and suspension which safely dissipates the forces causingboom recoil, while still maintaining stability of the inner section ofthe boom.

Since the intermediate portion of the boom which is usually subjected toflexing stresses is jointed in the present invention rather thanconsisting of a heavy, rigid structure, a much lighter boom constructionis possible, thereby permitting an increase in the total length of theboom without an increase in weight.

Having now described and illustrated two forms of the invention, it isto be understood that this invention is not to be limited to thespecific form or arrangement of parts herein shown and described.

What is claimed is:

1. In a dragline excavator having a main frame and a digging bucketsupported by a hoist line and moved for digging by a dragline thecombination therewith of: a multiple-section boom having a boom foot anda boom point; a boom-pivot connection with the main frame; said boomcomprising an inner section and an outer section having theirlongitudinal mes substantially in alignment; a pivotal connectionbetween the inner and the outer boom sections; suspension means betweenthe main frame and the outer endof the boom; an upwardly-inclined mastinterposed between the suspension means and the inner boom section; amast-to-boorn connection joining the mast to the inner boom section; afixed-length flexible tension member between the'mast at a point nearthe top of the mast and the boom at a point adjacent the pivotalconnection between the inner and thetouter boom sections; saidsuspension means comprising variable-length boomhoist tackle between themain frame and the mast and comprising a fixed-length flexible tensionmember between the mast and the boom adjacent the boom point; both ofsaid fixed-length flexible tension members being dimen sionedproportionately in such a manner that the boom sections are maintainedin substantial alignment; and the said mast-to-boom connection being solocated outwardly from the boom-foot pivot a substantial predetermineddistance and the mast inclined in such a manner that the line of actionthrough the mast imparts a downward moment to the inner boom section andthereby maintains the ten sion member in tension at all times throughoutthe range of boom positions.

2. In a dragline excavator, the construction according to claim 1,further characterized by the fact that the mast comprises a plurality ofstruts angularly spaced in a vertical longitudinal plane of the boomeach being connected at one end to the inner boom section by means ofthe mast-to-boom connection, the upper ends being connected by a portionof the suspension means, and a plurality of stiffening membersinterconnecting said struts at a plurality of points intermediate theends of said struts.

3. A dragline excavator according to claim 1, further characterized bythe fact that the downward moment imparted to the inner boom sectionthrough the line of action of the mast is not less than one-tenth norgreater than one-half of the upward moment through the line amen-ea thesaidinner boom section; a fixed-length flexible ten-I sion memberconnecting the mast near its upper end and, the boom adjacent thepivotal connection ofthe boom sections; a mast to-boom connectionpivotally joining the mast to said inner section and located at a pointintermediatethe 'ends of said inner boom section; the respectivelocations of the anchorage, the boom pivotv connection,- and themast-to-boom connection being spaced in such a manner that for ahorizontal position of the boom, the distanc'e' between the anchorageand the mast-to-boom connection is greater than the distance between theanchorage and the boom pivot thereby providing a wide angle between themast and that portion of the suspension means between the mast and theanchorage and reducing the compression stress on the mast.

5. In a dragline excavator, the construction according to claim 4,further characterized by the fact that the mast in a vertical planepassing through the longitudinal axis of the boom is in the form of aninverted triangle.

6. In a dragline excavator, the construction according to claim 5,further characterized by the fact that the inner section of the boom ina vertical plane passing through the longitudinal axis of the boom is inthe form of an upright triangle. 7

7. In a dragline excavator: a boom and suspension means, comprising amain support base; an elevated anchorage on the main base; a boom havinga boom foot and a boom point; said boom comprising an inner section andan outer section; a pivotal connection between said sections; aboom-pivot connection between the main base and the boom, adjacent thefoot of the boom; suspension means for the boom connecting the anchorageand the boom; an upwardly-inclined mast interposed between thesuspension means and the boom; a fixed-length tension member connectingthe mast near its upper end and the boom adjacent the pivotal connectionof the boom sections; a mast-to-boom connection pivotally joining themast tothe inner boom section; saidmast-to-boom connectionbeing spacedoutwardly from the boom foot 8. sufficient distance so' that a downwardmoment is imparted to the:inner boom .section about the, boom foot; themast in a vertical plane passing ,through the longitudinalaxisrof theboom being inmtheform of an inverted triangle; the base of saidinvertedtriangularly-shaped mastbeing connected to the suspension means;the apex of said mast beingconnected to the inner boom section; and thedimensions of the triangular mast, the length of the boom and therespective locations of the anchorage, the connection between thesuspension means and the boom, the boom foot pivot and the mast-to-boomconnection being so proportioned that approximately equal angles resultbetween the base of thetriangular mast and lines drawn through the linesof action of the suspension means on both sides of the mast when theboom is in an elevated, operating position v a 8. In a draglineexcavator, the construction according to claim 7, further characterizedby the fact that the inner section of the boom in a vertical planepassing through the longitudinal axis of the boom is in the form of anupright triangle.

9. In a dragline excavator, a multiple section boom and suspension meanscomprising a boom having an inner section and an outer section; ,apivotal connection between said inner and outer sections; a mainsupporting base; a pivotal connection between the main base and theinner section of the boom; an upwardly inclined mast connected to theinner sectionintermediate the ends of said inner section; suspensionmeans between the main baseand the upper end of the mast; suspensionmeans between the upper end of the mast and the outer end of said outerboom section; and intermediate fixed-length flexible tensionmeansbetweenthe mast and a point on the boom adjacent thejuncture of saidinner and outer sections.

References Cited in the file of this patent UNITED STATES PATENTS2,015,629 Knox Sept. 24, 1935 2,073,539 Shelton Mar. 9, 1937 2,080,163Busick, Jr May 11, 1937 2,574,646 Le Tourneau Nov. 13, 1 951 2,633,649Page .L Apr. 7, 1953 FOREIGN PATENTS 655,950 Great Britain Aug. 8, 1951

